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José Ignacio Álvarez Galindo, Full Professor of Chemistry Inorganic. School of Sciences of the University of Navarra.

A component of our current life

Thu, 10 Oct 2019 11:28:00 +0000 Published in Navarra Newspaper

José Ignacio AlvarezIt would be impossible to conceive of our lives today without lithium-ion batteries. Cell phones, laptops, tablets, cordless vacuum cleaners, drills, cameras, electric cars and a long list of other wireless devices are powered by these rechargeable batteries.

They arose in response to the scarcity of fossil fuels, derived from petroleum, and with the idea in mind that these systems should act as portable energy suppliers, while being able to store electrical energy provided by an external source . Large electronic equipment companies were always interested in obtaining rechargeable power supply devices that were increasingly smaller, safer, cheaper and less or not at all polluting.

Behind the market launch in 1991 of the first lithium-ion battery, there is an interesting research Chemistry , now recognized with the award Nobel Prize, which began with the primitive lithium metal batteries. In these, the negative electrode is the lithium metal, and the positive electrode is a material capable of acting as a host during the intercalation reaction. During battery use, the lithium metal is oxidized and the lithium ion produced moves through the electrolyte medium to the positive electrode, where the host species is reduced and the host species is inserted. When the battery is depleted and recharged, the redox process involves the host species being oxidized, the lithium ion being released and reduced at the negative electrode and deposited as lithium metal. Whittingham discovered the usefulness of titanium disulfide as a host, a novel material for the cathode design , which had the capacity to host lithium ions. This was a topotactic reaction, with reversibility and significant voltage. Goodenough improved the research on the cathode material, demonstrating that metal oxides of some transition metals, such as cobalt, generated even higher potentials.

However, the high reactivity of lithium metal caused problems in the production of these batteries. Moreover, lithium ions, deposited on the anode during charging, could grow, sometimes uncontrollably, and contact the other electrode, short-circuiting the battery and causing it to explode. Yoshino improved the system by changing the anode: instead of the highly reactive lithium metal, he used a carbon anode that could also intercalate lithium ions. Thus, he had designed the first lithium-ion battery, in which both anode and cathode are two insertion compounds. The lithium ion is disinserted from one electrode and inserted into the opposite electrode, depending on the charge-discharge stages. By not using lithium metal directly, the production of these batteries is simplified and the safety of their use is significantly increased.

The Chemistry continues to work in this field, in which the Nobel laureates have been pioneers. At present, alternatives to insertion materials are being sought, and systems have been developed with LiMn2O4 spinels, doped LiMn2O4 spinels, new carbon-based materials, lithium alloys, polymeric materials, tin oxides and alloys, etc. The electrolytic medium can also be modified. The drive for electric vehicles will force efforts in this field, looking for batteries with higher voltages and specific powers, lower weight and volume and higher cyclability, using cheaper, available and non-polluting materials.